Jun Jie Yang

Extraction of Schottky barrier height in Hg0.702Cd0.298Te photovoltaic infrared detector pixel arrays by transient photovoltage measurements

A novel method for extracting the Schottky barrier height (SBH) of a pn-junction-type HgCdTe photodetector by photovoltage measurement has been proposed. The photovoltages of the pn junction and Schottky junction are saturated by the bias light and transient laser pulses. The SBH is obtained as 0.228 eV, which is basically in agreement with the value obtained by the current–voltage technique. Because of the absence of complication due to the interference of the pn junction in the photovoltage measurement, this method is suitable for extracting the low SBH of the pn-junction-type photodiode, whose rectifying behavior of the Schottky contact is unclear.

Transformer Region Customer Information Detection System

Aim at solving the electricity customer unclear ownership problems in some old city area, the transformer region customer information detection system was designed, using low voltage power line carrier (PLC) technology to detect transformer of the connectivity of concentrator and the collector within their respective jurisdictions, and further determined the dependencies of the electric power customer and concentrator, displayed results in the information management server. The system consists of the customer information detection terminal and the customer information management software. The experimental results show that the system can actually solve the issues of mixed customer information under the complex line loss problem.

Transformer Region Customer Information Management System Design

In order to clarify the relationship between concentrator and collector in some Transformer Regions, the transformer region customer information management system was proposed based on a low voltage power line carrier technology. The system consists of the customer information detection terminal and the customer information management software. Detection terminal achieves the detection of relationship between concentrator and collector, within the scope of the common variants, through power line carrier communication technology, and sends the information to the information management server. Customer information management software managed the information ,which came from the terminal, using a database technology and displayed the results sorted, achieving the functions of detection terminal—parameter settings, data management, communication function, management functions for user rights. GPRS mobile public transport networks were used to keep communication between the terminal and information management software.

Assessment of Transmission Line Icing State Based on Multi-Sensor Information Fusion

Due to considerations limited for the current monitoring techniques and computational models and other reasons,the accuracy rate of line icing condition assessment is not high. Transmission line icing are affected by many factors, having greater relevance with micro-meteorological parameters. To improve the assessment accuracy of transmission line icing condition,multi-sensor information fusion method are put forward for a comprehensive assessment to Line icing state, based on online monitoring system,considering the equivalent ice thickness of monitoring system, micro-meteorological parameters and duration of ice cover.BP neural network convergence line icing membership value, the output state is cing probability. Then ,the probability of the state of uncertainty output line integrated assessmen through Fuzzy Reasoning

Design of Dual High Precision Power Signal Generator Based on AD9854

To obtain the dual high-precision numerical control signal source, and could be accurately adjusted the dual signals frequency and phase and increase the output signal power, the paper presented a method based on direct digital synthesis technology and parallel push-pull output, designed and implemented the dual channel high-precision and high power signal generator. MSP430 controlled AD9854 registers to realize frequency and phase modulation, after low-pass filter to adjust the square wave duty cycle by the DAC7612, amplitude was integrated optimization adjustment by AD9854 AD603 and power amplifier. Consideration the anti-jamming measures, the system is stable and reliable, and can output high-precision and high power sine and square wave in the 5-150kHz frequency band, signal frequency, phase, amplitude and duty cycle can numerical control. In addition, it has sweep output mode.

Nonlinear Dynamic Compensation for Probability Analysis in Fault Diagnosis of Electric Equipment

A nonlinear dynamic compensation for probability analysis in fault diagnosis of electric equipment was reported. Because of the limitations of Threshold temperature diagnosis method and the traditional Bayesian theory fault diagnosis method of electric equipment, a nonlinear SGompertz model and quadratic power model were used to compensate the diagnosis results for the influence of equipment aging and running temperature, then the maximum probability principle was adapted to judge whether the equipment is in malfunctioning state. The 3-D simulation results indicates that: (1) there is a strong relationship between the status and equipment aging and running temperature; (2) an obviously difference exists between linear and nonlinear compensational results of the characteristic temperature region. This proposed methodology is testified having important significance in improving the reliability and the information level of power transformers operation.

The Effect of Metal-Semiconductor Contact on the Transient Photovoltaic Characteristic of HgCdTe PV Detector

The transient photovoltaic (PV) characteristic of HgCdTe PV array is studied using an ultrafast laser. The photoresponse shows an apparent negative valley first, then it evolves into a positive peak. By employing a combined theoretical model of pn junction and Schottky potential, this photo-response polarity changing curves can be interpreted well. An obvious decreasing of ratio of negative valley to positive peak can be realized by limiting the illumination area of the array electrode. This shows that the photoelectric effect of Schottky barrier at metal-semiconductor (M/S) interface is suppressed, which will verify the correctness of the model. The characteristic parameters of transient photo-response induced from p-n junction and Schottky potential are extracted by fitting the response curve utilizing this model. It shows that the negative PV response induced by the Schottky barrier decreases the positive photovoltage generated by the pn junction.

Optical Limiting Using the Two-Photon Absorption Electrical Modulation Effect in HgCdTe Photodiode

The electrical modulation properties of the output intensity of two-photon absorption (TPA) pumping were analyzed in this paper. The frequency dispersion dependence of TPA and the electric field dependence of TPA were calculated using Wherrett theory model and Garcia theory model, respectively. Both predicted a dramatic variation of TPA coefficient which was attributed into the increasing of the transition rate. The output intensity of the laser pulse propagation in the pn junction device was calculated by using function-transfer method. It shows that the output intensity increases nonlinearly with increasing intensity of incident light and eventually reaches saturation. The output saturation intensity depends on the electric field strength; the greater the electric field, the smaller the output intensity. Consequently, the clamped saturation intensity can be controlled by the electric field. The prior advantage of electrical modulation is that the TPA can be varied extremely continuously, thus adjusting the output intensity in a wide range. This large change provides a manipulate method to control steady output intensity of TPA by adjusting electric field.

Study on Partial Discharge of Electric Equipment Based on Ultraviolet Imaging Technology

The application of Ultraviolet Imaging Technology (UVIT) in the electric equipment Partial Discharge (PD) was proposed and the operating principle of Ultraviolet Imaging Technology Instrument (UVITI) was analyzed in the paper. By describing the current development trend of UV imaging technology in China and foreign country, the several factors influencing the detect accuracy of the UVITI was analyzed. The results show that: the environment temperature, the back light, the air humidity, the instrument gain level, the wind level and the measurement distance will influence the accurate measurement of PD level and location seriously. In order to detecting the PD level and locating the fault position accurately, electric equipment PD measurement should be taken in low environment temperature and humidity, short measurement distance and avoiding big wind. For the disturbing of environment noise on measurement signal, the instrument gain level should be improved.

A New Wavelet-Based Compressive Sensing for Image Compression

Compressive sensing (CS) technique can capture and represent compressible signal at a rate below the Nyquist rate of sampling. In this paper, the compressive sensing principles are studied and a new wavelet-based coding method is proposed. Two-dimentional discrete wavelet transform (DWT) is applied for sparse representation. Then the wavelet coefficients are divided into four blocks and are compressed by four different sensing matrixes respectively. The recovery quality depends on the number of received CS measurements. Experimental results show that the proposed coding method achieving higher performance compared with the conventional wavelet-based compressive sensing coding system. With 50% coefficients retained, the image can still be recovered with considerably objective and subjective quality.